Low temperature engine-protecting device



D. .1. coNANT ET AL 1,932,064

LOW TEMPERATURE ENGINE PROTECTING DEVICE Oct. 24, 1933.

Filed June 19, 1930 ATTORNEY 'Patented oct. 24, 1933 UNITED STATES PATENT oFFicE LOW TEMPERATURE DEVIC ENGINE-PROTECTING Application June 19, 1930. Serial No. 462,391

8 Claims.

This invention relates generally to control systems for electric power plants, such as are used for farm lighting, the operation of airplane beacons or similar service.

More particularly, this invention relates to automatic electric-generating systems including, among other elements, a battery, an engine, a dynamo-electric machine and load-line circuits and adapted for use on automobiles, or in isolated places, such as country residences, farm homes, places where the attendant is partially or totally unskilled in the art of managing such plants, or generating plants for airplane beacons, which are often isolated and where the attendant, whether skilled or unskilled, merely makes periodic inspection of the plants to provide the necessary gasoline and oil.

An object of this invention is the provision of an electric-power unit which shall be simple in construction, automatic and efficient in operation and which may be readily installed.

A more specific object of the invention is to provide for protection of an internal-combustion engine against low temperatures.

A further object of the invention is-to provide for the automatic starting of the engine when the ambient temperature drops to a predetermined' value and for automatically stopping the engine when the temperature of the engine or the oil in the crank case or both have been raised to a predetermined value by operation of the engine alone, or by operation ofVV the control system, or by the combined operation of the control system and the engine.

Isolated power plants, as above designated, for very practical reasons, usually -use air-cooled engines. It is a well known fact that air-cooled engines operate at a much higher temperature than do water-cooled engines. To ensure proper lubrication of the engine during operation, the oil that must be chosen is an oil having rather high viscosity. All oils at present available in the market for air-cooled engines change their viscosity very much with changes in temperature. At the low atmospheric temperatures frequently occurring in winter, the oil in the crank case of an engine solidies and thus loses its lubricating quality entirely.

If, under such conditions, an attempt be made to start the engine, the load is so great that an excessive current is drawn from the battery, thus injuring it. If the engine fails to start, the battery may be completely discharged. The engine may start and burn out the bearings before the solidified oil is heated sufciently by the engine operation to again possess lubricating qualities.

Other objects and advantages will be apparent from the following specification, when considered in conjunction with the accompamling drawing.

While the following discussion of this invention relates more particularly to an air-cooled engine, the invention is, however, not limited to such engine but is also applicable to a liquid-cooled engine. Minor characteristics of design must in such case be changed. Broadly, therefore, the invention relates to means for protecting an internal combustion engine againstwlow temperature.

Fig. 1 is a diagrammatic showing of an automatic electric-generating system embodying the elements of this invention; and Fig. 2 is a modiflcation of a detail4 showing an electric heater and thermostats.

In the diagrammatic showing of the automatic electric-generating system, the numeral 1 designates a series line relay for automatically controlling the starting and the stopping of the engine E in response to load conditions in the load lines 12, and 32. Associated with the control system, and particularly with the series line relay 1, are a. pair of control relays 2 and 3 which control the starting operation of the engine through the dynamo-electric machine M, acting as a motor.

To protect against continuous cranking, in case the motor fails to start the engine, a thermoelectric time-limit relay 4 is provided. Associated with the engine, but more particularly with the carburetor of the engine, is an automatic-choking device 5 and an auxiliary timelimi-t choking device 7, and, intermediate the carburetor and the engine, is disposed a series governor 9. Reference character 8 designates another relay disposed for operation to isolate the battery B from the generating system in case the voltage decreases to a predetermined value either through excessive discharge of the battery or because of a short-circuit on the line.

The series governor 9, during operation of the engine E and machine M, controls the fuel supply, and the amount of fuel fed to the engine is proportional to the load on the line. However, during manual starting, effected through the operation of the push-button switch 6, the governor is held open to ensure an ample fuel supply.

Referring more particularly to the .elements in the drawing, 1 represents a series line relay and comprises an actuating coil 23, an amature 24 and a contact-bridging member 29 disposed for operation by the armature. The armature `24 may be biased towards a position in which the contact members o! the relay are open by means of a spring 26 positioned between an upper fixed support 25 and a washer 27 secured to the lower end o! the spring and held in any given position on the armature 24 by a nut 30 mounted on a screw-threaded extension 28 of the armature. The spring 26 and the armature 24 are secured against rotation.

The nut, below the washer and in threaded engagement with the extension 28 on the armature, is provided with graduations for cooperation with an index on the washer 2'7. By a manipulation oi the nut, the biasing eiect may be adjusted to any desired value and, in consequence, the current flowing through .the coil necessary to hold contact members 31 closed may be predetermined. The position of the nut 30 and, hence, the degree of compression initially applied to the spring when the relay is in the open position, will determine both the pull in" and the "drop out values of current ilowing in the coil 23 at which the relay will either close or open its contact members.

For example, if the nut 30 is adjusted to a certain position, for instance, the position shown in the drawing, a current of six amperes may be required to energize the coil to close the contact members of the relay 1. When the relay is closed, a current of less than six amperes will maintain it closed. Therefore, i! the current be reduced to a value below six amperes, a balancing point will be reached at which the magnetic pull of the coil on the armature will balance the pull of the spring on the amature. Ii.' the current be reduced still further, the force exerted by the spring will become greater than the magnetic pull ot the coil, and the relay will be actuated to open its contacts. The value of the coilenergizing current traversing the coil at which the relay will "drop out or open may be as low as three amperes.

In the drawing, B designates the battery, which is oi. the 32-volt type. However, it is obvious that the number of individual units of the battery may be changed so that any other voltage, such, for example, as 110, may be provided.

To provide for manual starting of the engine, a push-button switch 6 is provided. Conductor 100, stationary contact members 101, movable contact member 102 and conductor 103 provide a shunt circuit for the contact members 29 and 31 of the series line relay. Operation of the pushbutton switch thus causes establishment o1 starting connections for the power plant, regardless of whether there be a load on the lines 12 and 32 or not.

Connected directly across the battery terminals, is a low-voltage control relay 8 having an actuating coil 14 and contact members 13 disposed to open the load-line circuit to isolate the battery from the generating system in case of excessive discharge of the battery or because oi' the heavy current that may be drawn by the dynamoelectric machine M in case the rotor becomes locked during the starting operation. The circuit i'or the low-voltage relay may be traced from the positive terminal of the battery B, through conductor 11, contact members 13, actuating coil 14 of relay 8, conductor 15 and conductor 12, to the negative terminal oi the battery. Connected in series with the load line is an ammeter A which may be mounted on a panel board in some convenient place`for observation.

The actuating coil 20 o! the series governor 9 is connected in the conductor 19. 'I'he function of the series governor, during normal automatic operation, is to open the valve in housing 86 in direct proportion to the load current. As shown, the actuating coil 20 acts directly on armature 85.

The low temperature protective cranking device 79 consists of an electric heater 88 disposed in a housing 93 which is inserted in the oil contained in the lower part of the engine crank case. At a different point in the body of oil in the crank case is disposed a thermo-responsive device consisting of a bimetal strip 91 cooperating with a contact member 90. The heater and thermostat may, however, be constructed as a single unit to be inserted through one opening in the crank case. 'Ihe bimetal strip is designed to swing downwardly to make contact at 94 to establish a circuit through the electric heater 88 when the temperature of the oil in the crank case drops to a predetermined temperature, in this case about 25 to 15 F. However, the thermostat may be adjusted to cause the establishment oi' the heater circuit at any desired temperature. At about 20 F., most oils used for air cooled engines still have suilcient lubricating properties to prevent burning out of the bearings and also prevent a too rapid drain on the battery during starting operation.

When the oil in the engine crank case is at a temperature of '10 to 90 F., the thermostat operates to interrupt the circuit through the heater 88. It is, of course, understood that the thermostat, consisting of the elements 90 and 91, is shown schematically. In practice, a Spencer thermostat or any other thermostat equally as serviceable may be used, or a pair of thermostats responsive to high and low temperatures, respectively, may be used. Furthermore, the combined resistance oi' the conductor 87, heater 88, conductor 89, elements 90 and 91 and conductor 92 is such that, upon establishment of contact at 94, the current through coil 23 is always large enough to operate the series line relay 1 and thus initiate starting operation.

In Figs. 2 a single unit is shown including the heater 88 and the housing 93 therefor and a paliof thermostats 91 and 91. The elements are shown in the position they would occupy when the engine is neither heated nor too cold. The thermostat elements 91 and 91' thus act in opposition and the element 90 is not actuated. At a predetermined low engine-oil temperature thermostat element 91 moves downwardly and since the force of thermostat element 91 is, for all temperatures, except a predetermined high temperature, in the downward direction, the circuit for the heater 88 is closed at 94. The engine is thus started as explained elsewhere in this specification. As the oil gets warmer the element 91 will ilrst act in an upward direction but since element 91 is still acting in a downward direction the circuit for the heater 88 will remain closed at 94. At a predetermined high engine-oil temperature element 91 will also act upwardly, thus permitting element 90 to break the circuit of the heater at 94 and thus stop the engine.

Controlled by the operation of the series line relay 1, is a time-limit thermo-electric protective cranking device 4 comprising a pair of bimetallic strips 69 and '70 rigidly fixed, at one end, to a support. To the free end of the strips 69 and 70 is loosely secured a push rod 98 to engage a latch member 105 held in a given position against a support 104 by means ot a spring 106.

' subject to the voltage of the generating system.

Wound about the bimetallic strip is a current coil 82 connected in the system to carry either the starting current drawn by the dynamo M, operating as a motor, or the current generated by the dynamo, when functioning as a generator, during loaded operation of the system.

Attention is called to the fact that heater 82, while wound about the bi-metallic strip 70, is nevertheless in the vicinity and in heat-transfer relation to the bi-metallic strip 69. The purpose of this arrangement is to compensate for any change in voltage that may take place in the system. For instance, if the heating effect of the heater 77 be insufficient, because of low battery voltage caused by an excessive current discharge from the battery, to cause a deflection of the bimetallic strip 69 through a given range in a required predetermined interval of time, the heater 82 causes sufficient heating of bi-metal strip 69 to provide for the required deflection.

When the engine is Warm, for instance, at 70 F., and the oil, in consequence is not viscous, the cranking current will be small and the voltage of the battery will not be affected appreciably during cranking. The heater 77 is, therefore, subject to normal battery voltage and, since the heating effect of heater 82, under these conditions, is negligible, will cause operation of the protective cranking device after a predetermined interval of time.

When the engine is cold, for instance, at 32 F., and the oil is correspondingly more viscous, the cranking current will be much greater, and the voltage of the battery impressed on heater 77 will be somewhat lower. Under these conditions, the effect of heater 82 is appreciable and, by its collateral heating of strip 69, aids heater 77 sufficiently to cause deflection of this strip over a predetermined range during the same interval of time required for the higher temperature. Heater 82 thus compensates for any drop of voltage of the battery during cranking.

If, during starting operation, the engine shaft should be locked and thus the voltage applied to the motor be across a stationary armature, the current would be excessive, and in consequence, the voltage of the battery would be quite low. Under such conditions, the effect on the heater 77 might not be sufficient to cause the protective cranking device 4 to function in time to protect the armature circuit and other circuits of the system. The heater 82, therefore, ensures a rapid actuation of the protective cranking device under such conditions.

Adjacent to the bi-metal strips 69 and 70 is disposed a support 109 having a screw-threaded projecting stem 113 carrying nuts 112 and a spring 111, the tension of which may be adjusted by the nuts 112. Intermediate the spring and the support 109, is disposed a contact-carrying member 110 having a relatively large opening through which the stem 113 extends. The member 110 may thus be moved towards the right, as on a pivot, and is biased to a given position against the support 109 by spring 111.

Intermediate the ends of member 110, is positioned a contact 99 for engagement with a contact 35 when the member 110 is in the position shown in the drawing. Upon deflection of either one or both of the bi-metal-strips 69 and 70. latch member 105 is moved to a lower position so that the projecting portion 115 on the latch member 105 extends into the opening'114, thereby opening the contacts 35 and 99. As soon as projection 115 enters the opening 114, latch member 105 cannot operate 4to close the contacts 35 and 99 and, if the protective cranking device has functioned, it is necessary for an attendant to reset the members 105 and 110 in the position shown.

Also controlled by the series line relay 1 are a pair of control relays 2 and 3. The control relay 2, including the actuating coil 44, contact members 45 and contact-bridging member 46, operates, after the actuation of the series line relay, to close a circuit for the dynamo M.

The relay 3 is provided With a pair of actuating coils 49 and 50, the actuating coil 49 being subject to the voltage of the battery and the actuating coil 50 being subject to the cranking current taken by the dynamo M, when operating as a motor. During cranking operation, the magnetic effect of the coils 49 and 50 is cumulative and operates to close the contact members 73 by the contact-bridging member 74.

After the engine has started and drives the dynamo M as a generator, the current in the actuating coil 50 reverses and thus its magnetizing effect is in opposition to the magnetizing effect of the voltage coil 49. The compound-wound relay 3 controls the current passing through the heater 77, the actuating coil 61 of the enginechoking device 5 and the heater 65 of the timelimit engine-choking device 7. If the engine starts before the protective cranking device 4 operates, contact members l73 are opened, and the circuits to actuating coil 61 and the heaters 65 and 77 are broken, as desired.

The operation of our low-temperature protective device is as follows:`

Assuming that the load drawn at L is insufflcient to operate series line relay 1, or that no load at all is drawn at L, and the temperature of the crank-case oil drops to 20 F., the thermostat 91 in the crank case makes contact at 94. A circuit is thereby established from the positive terminal of the battery, through conductor 11, contact members 13 of low-voltage protective device 8, conductor 17, ammeter A, conductor 19,'

actuating coil 20 of the series governor 9, conductor'21, actuating coil 23 of series line relay 1, conductors 32 and 87, electric heater 88, conductor 89, contact member 90, bimetal thermostat 91 and conductors 92 and 12, to the negative terminal of the battery.

Since the current in the low-temperature protective device exceeds a predetermined value, as above explained the series line relay closes contact members 31, thereby establishing a circuit from the energized conductor 32, through contact members 31, bridged by the contact-bridging member 29 and conductor 34, to contact member 99. Snce, during the starting operation, the elements of the protective cranking device are in the position shown in the drawing, contact members 35 and 99 are in engagement, thereby establishing three parallel circuits.

The circuit for the engine ignition is establshed, through conductor 36, primary winding 37 of the transformer of the ignition system 10, condenser 38 and interrupter 39 in parallel and conductor 12, to the negative terminal of the battery. The primary winding 37 and the secondary winding are disposed in inductive relation and have connected thereto a pair of conductors 42 leading to the engine block and spark terminal 41, respectively.

'Ihe second parallel circuit. established through the contacts 35 and 99, may be traced, through conductor 43, actuating coil 44 of control relay 2, conductor 47, actuating coil of the compound-wound relay 3, conductor 51 and conductor 12, to the negative battery terminal.

The coils 44 and 49 are connected in parallelcircuit relation by means of conductors 48 and 47. During this stage of operation, the effect of the cols 49 and 50 is additive. However, before the actuation of the control relay 2, the combined magnetic etIect of coils 49 and 50 is not sufncient to connect the contact members 73 by the bridging member 74.

The control relay 2, upon energization, however, operates to close contact members 45 by the contact-bridging member 46, thereby establishing a motor circuit for the dynamo-electric machine M. This circuit may be traced from the positive battery terminals, through conductor 11, contact members 13 of the low-voltage protective device 8, conductor 17, ammeter A, conductor 18, heater 82, conductor 52, series field winding 53, conductor 54, armature 55 of the dynamo M, conductor 56, contact members 45-bridged by the contact bridging member 46, conductor 47, actuating coil 50 and conductors 51 and 12, to the negative terminal of the battery.

Disposed in parallel-circuit relation to the armature 55, is a shunt field winding 57, a. shunt eld resistor 58 and a conductor 59.

Closure of the contact members 45 by the contact-bridging member 46 and the establishment of the circuits just described causes the heavy cranking current to pass through actuating coil 50. 'I'he combined magnetic effect of coils 49 and 50 thus operating to close contact members 73 by the contact-bridging member 74. Closure of contacts 73 establishes a circuit from contact member 35 to contact member 99, conductor 72, contact member 73-bridged by the contact-bridging member 74 of the compound wound relay 3 and conductor 75, through a plurality of parallel circuits and through the protective time-limit engine-cranking device 4, the engine-choking device 5 and the time-limit engine-choking device 7. These circuits may be traced from the energized conductor 75, through conductor 76, heater 77, conductor 78 and conductor 12, to the negative battery terminal and, through conductor 60, actuating coil 6l of the engine-choking device 5, conductor 62, conductor 63, conductor 78 and conductor 12. to the negative terminal of the battery and also from conductor 75, through conductor 64, heater of the time-limit engine-choking devce 7, conductor 63 and conductors 78 and 12, to the negative terminal of the battery.

Normally, the engine starts within a given time after the operation of the series line relay 1, the current in the actuating coil 50 reverses, opposing the elect of the coil 49 and thus causing the separation o! the contacts 73. 'I'his operation of contacts 73 prevents the protective cranking device from functioning.

Operation of the engine heats up all the operating parts and also the lubricating oil in the crank case. Obviously, if the engine should operate long enough and the heat dissipation be not too great, the thermostat 91 would function independently of the heater 88. In practice, however, it has been found that the heater 88 cooperates in a very beneficial and novel manner with the engine and the thermostat.

After the,` engine starts, the operating parts heat up at a comparatively rapid rate, while the heater 88, continuing to operate, raises the temperature of the oil in the crank case in a short interval o! time. The engine thus operates for a short interval of time, until the operating circuit is interrupted at 94, and then stops. If the low ambient temperature persists, the cycle described repeats itself. Forthe ordinary low temperatures occurring in the United States during winter nights, it seldom happens that the plant need start itself more than once during a night.

We do not limit ourselves to the specific structural details, arrangement of parts or circuit con nections herein set forth, as various-other modlflcations thereof may be made without departing from the spirit and scope of this invention, as denned in the appended claims.

We claim as our invention:

1. In combination with an internal-combustion-engine-operated generating unit of the demand-starter type having load lines and a control relay for starting and stopping the generating unit dependent on a demand at the load lines, said engine being adapted to contain oil in the crank-case thereof, a circuit connected across the load lines to control the control relay, an electric heater inserted in the oil in the crank case of the engine and connected in series with the circuit, a thermostat inserted in the oil in the crank case of the engine for closing the circuit connection when the oil is at a predetermined low temperature, and a thermostat for interrupting the circuit when the temperature of the oil and engine has risen to a predetermined high degree.

2. In combination with an internal-combustion-engine having a crank case adapted to contain lubricating oil for the engine and having a starter, a heater in the crank case for heating the oil, and a thermostat in the oil for connecting the heater as a load to operate the starter, when the oil is at a predetermined low temperature and for stopping the functioning of the engine and heater when the oil is at a predetermined high temperature.

3. In combination with an internal-combustion-engine operated electric generating unit of the demand-starter type having load lines and a control relay for starting and stopping the generating unit in response to demand at the load lines, said engine having a` crank case adapted to contain lubricating oil for the engine, an electric heater in the crank case, a thermostat for coi'f necting the heater to the load lines when the oil is at a substantially predetermined low temperature, thereby causing operation of the control relay, and a thermostat for disconnecting the heater from the load lines and for stopping the engine when the oil is at a substantially predetermined high temperature.

4. In combination with an inter'al-combus tion-engine-operated generating unit of the demand-starter type having load lines and a control relay for starting and stopping the generating unit dependent on a demand at the load lines, a load unit comprising an electric heater, and thermostatic means responsive to predetermined low and high temperatures respectively to connect the heater in circuit relation with the control relay to start the generating unit and to disconnect the heater from the control relay to stop the generatingunit.

5. In combination with an internal-combustion-engine-operated generating unit of the demand-starter type having load lines and a control relay for starting the generating unit dependent on a demand at the load lines, a load unit comprising an electric heater, and thermostatic means responsive to a predetermined temperature to connect said heater to the load lines to effect the operation of the control relay to start the generating unit.

6. In combination with an internal-combustion-engine-operated generating unit of the demand-starter type having load lines and a control relay for stopping the generating unit dependent on conditions of demand at the load lines, a load unit comprising an electric heater for heating the engine, and a thermostat responsive to a predetermined engine temperature to disconnect said heater from the load lines to effect the stopping of the generating unit through the control relay.

'7. In Vcombination with an internal-combustion-engine-operated generating unit of the demand-starter type having load lines and a control relay for starting and stopping the generating unit dependent on conditions of demand at the load lines, a load unit comprising an electric heater for heating the engine, and a thermostat responsive to selected predetermined engine temperatures to connect and disconnect said heater from the load lines to thus eiect the starting and stopping respectively, of the generating unit through automatic control of the control relay.

8. In combination with an internal-combustion-engine-operated generating unit of the demand-starter type having load lines and a control relay for starting and stopping the generating unit dependent on a demand at the load lines, a load unit disposed to heat the engine, temperature responsive means mounted in the engine to be thus protected from rapid changes in ambient temperature but to be responsive only to a predetermined low engine-temperature for connecting said load unit in the load lines to cause operation of the control relay to start the generating unit, said means being also responsive only to a predetermined high engine-temperature to cause the control relay to function to stop the generating unit. l DAVID J. CONANT.

LEO C. FRANK. 

